1. Field of the Invention
The present invention relates to a wafer processing method of dividing a wafer such as a semiconductor wafer and an optical device wafer into a plurality of individual chips.
2. Description of the Related Art
As a wafer processing method of dividing a wafer into a plurality of individual chips, attention has conventionally been focused on a technique of dividing the wafer by laser processing. As an example of this laser processing, there has been proposed a processing method of applying a laser beam having a transmission wavelength to the wafer to thereby form a weak layer (modified layer) inside the wafer, wherein the modified layer reduced in strength functions as a division start point (see Japanese Patent No. 3408805, for example). In the processing method described in Japanese Patent No. 3408805, the laser beam is applied along a plurality of crossing streets formed on the front side of the wafer to linearly form the modified layer inside the wafer along each street. By applying an external force to the weak modified layer formed inside the wafer along each street, the wafer is divided along each modified layer to obtain the individual chips.